1. Field of the Invention
The present invention relates to a pulley device. More particularly, it relates to an improvement in a pulley device of an AC generator for a car.
2. Description of Prior Art
FIGS. 1 and 2 illustrate the conventional pulley device for an AC generator for a car. In the figures, the reference numeral (1) designates an steel plate which is formed by stamping and has a through-hole (1a) for receiving a shaft at the central portion and (2) designates the other steel plate which is associated with the former steel plate (1) to form a V-groove (3) and which is formed by stamping into a shape the same as the former steel plate and has a through-hole for receiving a shaft (2a) at the central portion. (4) designates a V-belt wound on the V-groove (3) and (1b), (2b) designate contact surfaces of the steel plates (1), (2) welded by mutual friction.
In preparing the conventional pulley device, the steel plates (1), (2) having the same shape are formed by stamping and one of the steel plate (1) is rotated under the condition that the contact surfaces (1b), (2b) of both the steel plates (1), (2) are in press contact as shown in FIG. 2 to produce frictional heat between the contact surfaces (1b), (2b) so as to melt-bond the steel plates (1), (2), thereby fabricating a pulley device having the V-groove (3).
In the conventional pulley device obtained by friction welding, steel plates (1), (2) are molten by the frictional heat and solidified. In other words, the steel plate are once heated to the melting temperature and then cooled, whereby heat stress is easily produced. This causes deformation of the shape of the V-groove (3) which severely wears the V-belt (4). Sometimes, the V-belt (4) is dropped out the V-groove (3).